[gdal-dev] Creating a VRT dataset from overviews in C++

[Dmitry Baryshnikov]

10.05.2012 19:03, tseval ???????:
> Hi,
>
> I'm trying to cut and reproject a large image with overviews using the c++
> api. This runs extremely slow when I produce highly downsampled cutouts
> covering large areas of the original image.
>
> I understand the the Warp API doesn't use the overviews when resampling, so
> I wanted to make a temporary dataset from one of the downscaled overviews
> and do the warping on this dataset instead.
>
> First of all, is this a sensible way of doing things? If so, what driver
> should I use? I guess VRT? I have been trying to create a VRT by doing
> something like this:
>
> 	double scaleX = (double)ovrW/origW;
> 	double scaleY = (double)ovrH/origH;
> 	GDALDataset* vrtDS = vrtDriver->Create("", ovrW, ovrH, _numBands,
> _dataType, NULL);
> 	GDALSetProjection(vrtDS, _srcProjectionWKT);
> 	double geoTransform[6];
> 	srcDS->GetGeoTransform(geoTransform);
> 	geoTransform[XFM_PIXEL_SIZE_EW] = scaleX*geoTransform[XFM_PIXEL_SIZE_EW];
> 	geoTransform[XFM_PIXEL_SIZE_NS] = scaleY*geoTransform[XFM_PIXEL_SIZE_NS];
> 	vrtDS->SetGeoTransform(geoTransform);
>
> But how am I supposed to set the bands in the VRT from the downscaled
> overview bands in the original image?
>
> Any help on this would be greatly appreciated :)
>
>
> --
> View this message in context: http://osgeo-org.1560.n6.nabble.com/Creating-a-VRT-dataset-from-overviews-in-C-tp4965891.html
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>
Hi,

You can try to use this patch to enable overviews in VRT 
http://trac.osgeo.org/gdal/ticket/2076
or waits as I accomplish my work on fixing this 
situation.<http://trac.osgeo.org/gdal/ticket/2076>

Best regards,
     Dmitry
<http://trac.osgeo.org/gdal/ticket/2076>
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